将位置 / gps 坐标写入文件

Question

好吧，我知道这听起来可能很简单，但我确实到处寻找，但找不到直接的答案。每次获得更新时，我都会尝试将位置坐标保存到文件中 - 听起来很简单....我有两个问题：一个是数据类型（writeToFile 似乎只保存 NSData），另一个是附加到文件的结尾。我尝试使用 NSKeyedArchiver，但它写了一堆垃圾，我找不到如何用它附加到文件末尾。

这是我的代码 - 如果您能提供帮助，我将不胜感激。谢谢！

....

NSMutableArray *array = [[NSMutableArray alloc] init];
NSNumber *numLat = [NSNumber numberWithFloat:location.coordinate.latitude];
NSNumber *numLong = [NSNumber numberWithFloat:location.coordinate.longitude];


[array addObject:numLat];    
[array addObject:numLong];    

NSFileHandle *file;
file = [NSFileHandle fileHandleForUpdatingAtPath: @"./location.txt"];

if (file == nil)
    NSLog(@"Failed to open file");


[file seekToEndOfFile];

[file writeData: array]; //BTW - this line doesn't work if I replace array with numLat which is an NSNumber - unlike what many people have said in various discussions here

OR - 保存到文件部分（最后两行）：

NSString *path = @"./location.txt";
[NSKeyedArchiver archiveRootObject:array toFile:path];

Answer 1

// Get the path to the Documents (this is where your app saves data)
NSArray *searchPaths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsPath = [searchPaths objectAtIndex: 0];
[array writeToFile:[documentsPath stringByAppendingPathComponent:@"location"] atomically:YES];

要将数据加载回数组，请使用

NSArray *searchPaths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsPath = [searchPaths objectAtIndex: 0];
array = [[NSMutableArray alloc] initWithContentsOfFile:[documentsPath stringByAppendingPathComponent:@"location"];